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Drones — especially the quadcopter
variety — are hot. Not only are
they cool to watch and to fly, but
they're excellent R&D platforms for
robotics. In this article, I'll examine
the Parrot AR Drone 2.0 ('AR
Drone'): an entry-level quadcopter
that can give you an introduction
to the many advanced technologies
under development for the larger
quadcopter platforms. Figure 1

shows the lower fuselage of the
AR Drone with the expanded
polypropylene indoor hull overlaid.

Quadcopters

If you’ve been to one of the Maker or SparkFun fairs
recently, you know that quadcopters rule when it comes to
autonomous vehicle competitions. One reason for the
interest in quadcopters is that — when properly designed —
they are the epitome of mechanical elegance. Instead of
the complicated gyros and gearboxes of a helicopter or the
ailerons and other control surfaces of an airplane, there are
four fixed electric motors and props. Change the relative
speeds of the props and you control the flight of the craft.

This elegant, efficient platform is possible because the
simple hardware is paired with powerful software, and
because of the consistent availability of high speed
brushless motors and electronic speed controllers (ESCs).
Figure 2 shows one of four integrated ESC/brushless motor
assemblies on the AR Drone.

You don’t need a degree in mechanical engineering
and access to a machine shop to design and build a
quadcopter. You do need to understand sensors, their
limitations, and some advanced sensor handling algorithms
if you’re going to design your own. Figure 3 shows the
underbelly of the AR Drone. From the top to bottom of the
image are the low-res camera, ultrasonic range finder, and
720p camera.